Neuropathological changes such as, in particular, degenerative or vascular changes with different causes in specific brain regions cause possible dementia. A comprehensive examination of dementia which is as accurate as possible also requires imaging methods in addition to clinical, neuropsychological and laboratory tests. Magnetic resonance imaging—abbreviated MRI—and nuclear medical imaging—abbreviated NM—are usually used for this purpose. Their reliability varies depending on the type and characteristics of the dementia. For example, the onset of Alzheimer's disease can be verified in the early stages using the nuclear medical method known as positron emission-tomography—abbreviated PET. In this case, the glucose metabolism of the brain is visualized on the basis of 18-fluorodeoxyglucose (i.e. a radioactively marked glucose)—abbreviated FDG. A brain region with vascular change due to circulatory disorders often manifests itself in the so-called white matter of the brain, which can be displayed in MRI, but not as well with PET based on FDG. Depending on the illness or the stage of the illness, either MRI or PET is better; the symptoms of the two illnesses can be very similar. Often the examination is concluded after carrying out one of the two previously mentioned imaging methods, if an indication of dementia is diagnosed. A second illness present at the same time is not detected. Among the reasons for this are a high expenditure of time and limited cooperation of the respective patients. It is clear that the detection of such brain regions can only be implemented with the aid of electronic imaging and image evaluation methods and machines, that is to say generally with the aid of computers.
Since it is often the case in patients that hybrid forms of dementia are present or have to be excluded, it could often be necessary to carry out both a PET and MRI for a precise examination. Both methods require a high expenditure of time and require cooperative patients who are able to lie still on two, occasions for approximately 30 min. In the case of a patient group with the presently described illness, this is often not possible or is possible only after the administration of sedatives. The latter could in turn influence the PET. These examination procedures sometimes place an enormous strain on both the patient and the medical staff.
Previously, only one of the two examinations was carried out in the daily clinical routine, which carries the possible risk of an incomplete examination. Alternatively the two examinations were carried out with large logistical effort—differing from patient to patient—and with the aid of sedatives, if applicable. Due to the required expenditure of time, the risk of movement artifacts, and hence insufficient image quality, is increased in the case of two sequentially carried out examinations. An appropriate method for improving the image quality is described in DE 10 2005 023 907 A1.